My latest 3D print. My mini rocket. The SPRO MKII, a redesign of my last one. With launch guide in the fin and easy loading/reloading system. So far untested. My aim was to make the smallest, lightest, most aerodynamic rocket I could. Weighing a total of 8.5 grams.

looks good. But if you want to save more weight you could just have 3 fins, with the added benefit that the rocket would always be stable no matter how flat the launch surface. But I guess the launch guide takes care of this latter point.

I don't know anything about model rockets, or real rockets for that matter, but have you thought about modeling in a curve to the fins to induce spin? Similar to rifling on a bullet? Might help to stabilize it in flight, though you would probably have to experiment with the rate of twist. Looking forward to seeing this one fly when you post a video.